1. Field of the Invention
The present invention relates to a reflective type display apparatus which is capable of performing display in color.
2. Description of the Related Art
In recent years, liquid crystal displays have been widely used as a flat display in view of its small size and light weight. Among others, a reflective type liquid crystal display apparatus, which does not require a back light system, has been attracting attention due to its low power consumption. An example of such a reflective type liquid crystal display apparatus is a TFT-LCD (Thin-Film Transistor-Liquid Crystal Display) reported on P.437 in the Proceeding of the SID (Society of Information Display) 92.
As shown in FIG. 8, the above-described TFT-LCD has a structure in which a drain electrode 84 of a TFT 81 and a pixel electrode 82 made of aluminum (A1) connected to each other through an interlayer insulating film (passivation film) 83. The pixel electrode 82 functions as a reflector having concavities and convexities corresponding to concavities and convexities formed on the surface of the interlayer insulating film 83. The light reflected by the reflector (the pixel electrode 82) is modulated by a guesthost type liquid crystal 85 containing dichroic dyes, and forms a color image through color filters 86.
Japanese Laid-Open Patent Publication No. 4-267220 discloses a reflective electro-optic apparatus as shown in FIG. 9. In this apparatus, concavities and convexities 91 are formed with an organic film in which fine particles are dispersed, and a metal layer 92 is formed thereon as a reflective layer. The reflected light from the metal layer 92 is modulated by a guest-host type liquid crystal 93 to display an image.
According to the TFT-LCD of FIG. 8, the fabrication steps are complex and the fabrication cost is expensive, since the concavities and convexities should be formed on the interlayer insulating film 83. Moreover, it is difficult to control a photolithography step in order that the concavities and convexities are formed on the interlayer insulating film 83 with a good reproducibility. Furthermore, since it is difficult to form very small concavities and convexities, the size of which is in the order of a micrometer, an excellent reflection characteristic can not be obtained.
According to the apparatus of FIG. 9, relatively small concavities and convexities 91 are easily formed by dispersing the fine particles in the organic film. However, since the reflection from the surface of the metal layer 92 induces a glare problem and makes it difficult to obtain excellent white display. In addition, color display, which will have a great demand in the near future, is not considered in this apparatus.